Method for solidifying and sealing in a toxic substance with sulfur

ABSTRACT

A method for manufacturing materials solidified with sulfur, comprising the steps of bringing the water content of a mixture of sulfur and a raw material to less than 3% by weight, heating and mixing the mixture of raw materials including molten sulfur at 119 to 159° C., to cause the sulfur to penetrate and encapsulate the raw material that is solid or liquid at the molecular level, thereby preparing a fluid mixture, and, if necessary, then molding the mixture into a desired shape or cooling it into a granular form.

This application is a divisional of application Ser. No. 08/982,469,filed on Dec. 2, 1997, now U.S. Pat. No. 6,083,431, which was aContinuation-In-part of application Ser. No. 08/653,348, filed May 24,1996, now abandoned, the entire contents of which are herebyincorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention generally relates to a method for solidifying andsealing in a toxic substance by using sulfur.

The present invention relates to a method for solidifying and sealing(blocking) in a toxic substance with sulfur, to detoxify that toxicsubstance. More specifically, the present invention relates to a methodof solidifying and sealing in a toxic substance including, but notlimited to, organochlorine compounds, such as PCBs, and heavy metals,with sulfur, to detoxify that toxic substance, additionally to obtaintherefrom a molded product that may be reusable.

Further, the present invention relates to a method of manufacturingmaterials made of raw materials particularly waste materials such asslag and/or dust resulting particularly from metal processing such assteel-making, and solidified with sulfur. More particularly, the presentinvention relates to a method of manufacturing molded materials made ofraw materials particularly waste materials such as slag and/or dustresulting particularly from metal processing such as steel-making, andsolidified by sulfur.

The term “molded materials” used herein refers collectively to materialsmolded into various shapes, as well as materials cooled with water orsome other method into a granular form, which can be used as is, orlater melted and molded into various shapes, for various purposes.

2. Background of the Art

Conventionally, slag and/or dust resulting particularly from metalprocessing such as steel-making, as well as other waste materials, etc.,are directly discarded in a site for waste materials disposal because asuitable treatment method has not been found. However, recently, with aview to reducing and/or detoxifying waste materials and, additionally,effectively utilizing resources, reduction and/or detoxification ofwaste materials and, additionally, utilization of reclaimed resources,that is, recycling of resources, is noted and studied. The need forestablishing a concrete and practical technique for reducing ordetoxifying waste materials and, additionally, recycling of resourceshas been pointed out.

Given the above background, reclaiming and utilizing or solidifying andsealing waste materials, such as fly ash and slag resulting particularlyfrom metal processing such as steel-making, has been studied in variousways. However, a satisfactory method has not yet been developed.

The present inventors, having keenly studied in various ways the methodand apparatus, found that it was not always practically easy to obtainmaterials solidified with sulfur and, if necessary, molded, by meltingsulfur at high temperature and mixing it with waste materials under hightemperature. The present inventors also found that there were someproblems in the conventional method regarding the quality of moldedmaterials solidified with sulfur and operations to make the moldedmaterials.

In particular, products that resulted from solidifying fly ash withsulfur were low in physical strength and sometimes caused cracks.Further, when slag and/or dust resulting particularly from metalprocessing such as steel-making were mixed with melted sulfur under hightemperature for producing molded materials, in the presence of iron inthe slag and/or dust, irritating sulfurous acid gas was often generated.This adversely affected the molding operation environment, making adeodorizing apparatus indispensable to prevent secondary pollution bythe molding operation. In addition to the above, only molded materialsthat were unsatisfactory in physical strength were obtained, andsometimes the molded materials were cracked.

The following fourteen (14) patents were uncovered in the pertinentfield of the present invention:

1. U.S. Pat. No. 3,720,609 issued to Smith et al. on Mar. 13, 1973 for“Process For Treating Aqueous Chemical Waste materials Sludges AndComposition Produced Thereby” (hereafter “the '609 Smith Patent”);

2. U.S. Pat. No. 3,962,080 issued to Dulin et al. on Jun. 8, 1976 for“Sodium Sulfur Oxides Waste Materials Disposal Process” (hereafter “theDulin Patent”);

3. U.S. Pat. No. 4,108,677 issued to Valiga on Aug. 22, 1978 for“Process For Treating Waste materials Sludge From Combustion PlantDesulfurization Units And Comentitious Product of The Process”(hereafter “the Valiga Patent”);

4. U.S. Pat. No. 4,342,732 issued to Smith on Aug. 3, 1982 for “SludgeFixation And Stabilization” (hereafter “the '732 Smith Patent”);

5. U.S. Pat. No. 4,354,876 issued to Webster on Oct. 19, 1982 for“Utilization of Dry Scrubber Waste Materials” (hereafter “the WebsterPatent”);

6. U.S. Pat. No. 4,354,942 issued to Kaczur et al. on Oct. 19, 1982 for“Stabilization Of Mercury. In Mercury-Containing Materials” (hereafter“the Kaczur Patent”);

7. U.S. Pat. No. 4,844,815 issued to Ader et al. on Jul. 4, 1989 for“Stabilization Of Mercury-Containing Waste materials” (hereafter “theAder Patent”);

8. U.S. Pat. No. 5,304,706 issued to Hooykaas on Apr. 19, 1994 for“Fixing Agent For Fixing Organic And Inorganic Impurities ContainingMaterial, Method For Fixing Such Material And A Synthetic Clay Material”(hereafter “the Hooykaas Patent”);

9. U.S. Pat. No. 5,362,319 issued to Johnson on Nov. 8, 1994 for“Process For Treating Fly Ash And Bottom Ash And The Resulting Product”(hereafter “the Johnson Patent”);

10. Soviet Patent No. 761,437 (hereafter “the Soviet Patent”);

11. JP-B-2-30751 (“JP-B” means examined Japanese patent publication);

12. East German Patent No. 288,099 (hereafter “the East German Patent”);

13. JP-A-9-194737 (“JP-A” means unexamined published Japanese patentapplication); and

14. DE 37 07 257 A1.

The '609 Smith Patent discloses a process for treating aqueous chemicalwaste materials sludge and compositions produced thereby.

The Dulin Patent discloses a sodium sulfur oxide waste material disposalprocess.

The Valiga Patent discloses a process for treating waste materialssludge from combustion plant desulfurization units and cementitiousproduct of the process.

The '732 Smith Patent discloses sludge fixation and stabilization.

The Webster Patent discloses the utilization of dry scrubber wastematerials.

The Kaczur Patent discloses a stabilization of mercury inmercury-containing materials.

The Ader Patent discloses a stabilization of mercury-containing wastematerials. It is a method which involves a chemical reaction in whichsulfur is reacted with a base to form a sulfide which is then reactedwith the mercury to form a new compound, insoluble mercury sulfide,which is then encapsulated (at a macro level) with cement created fromcement dust and water.

The Hooykaas Patent discloses a fixing agent for fixing organic andinorganic impurity containing material, method for fixing such materialand a synthetic clay material.

The Johnson Patent discloses a process for treating fly ash and bottomash and the resulting product.

The Soviet Patent discloses a complex concrete mix modifier compositioncontaining acid vat residue of raw benzene fractionation, sodiumcarbonate and sulphite waste materials liquor to improve plasticity.

JP-B-2-30751 discloses a process for solidifying industrial wastematerial, which comprises coating industrial waste materials containingsulphates with synthetic or natural resins, and then solidifying theresultant coated matter by cement.

The East German Patent discloses a process and arrangement forconversion of sulphur waste materials into disposable products. Itextracts sulphur from combustion gases into a scraper belt trough andmixes with rust ash.

JP-A-9-194737 discloses a sulfur-asphalt composition being low inignitability, high in compression strength, resistant to granulation,and stable in solid state.

DE 37 07 257 A1 discloses a method for direct embedding of solidified,especially toxic and/or radioactive materials, especially waste,existing in a loose state, in a storage container. In DE 37 07 257 A1,sulfur is used in specific conditions, that is, in the presence of NaCl,KCl in high amounts, e.g. 40 to 50 wt %.

In the above patents, there are no disclosure or teaching of thesolidification and sealing of a toxic substance in a high concentration.

It is highly desirable to provide an efficient process which utilizeselemental sulfur, sulfur-based materials, sulfur-based compounds orsulfur-based substances for the safe disposal of matter, including butnot limited to, all toxic substances and other hazardous substances(solids and liquids) into a form that renders the matter non-toxic andadditionally reusable.

On the other hand, among toxic substances, although PCBs(polychlorinated biphenyls) were used as a heating medium, an oil fortransformers, etc., their use is now prohibited, except in some fields,since they remain in the environment for a long time and are highlytoxic to the human body. Environmental pollution from the outflow ofPCBs or the like from waste PCBs that have been used and stored,remains, however, a serious social problem.

To detoxify PCBS, the complete combustion method, the hydrothermaldecomposition method (supercritical method); the dechlorination method,wherein light or radiation is used, and the like can be mentioned, andthe final disposal place for waste PCBs, their incineration ash, etc.,is required to be provided with a water barrier structure or the like.Other toxic substances besides PCBs, such as organochlorine compoundsother than PCBs, are also required to be detoxified in the similarmanner or processed in a final disposal place. However, since all ofthese means requires high-cost facilities, it is pointed out that atechnique of detoxifying these toxic substances readily at a low costneeds to be established.

Under these circumstances, various investigations have been made tosolidify and seal toxic substances, including organochlorine compounds,such as PCBs. However, a method has not yet been developed that issatisfactory in that toxic compounds can be prevented from leaching out,and, in addition, in that the reclaimed product can be utilizedeffectively, for example, a method has not yet been developed where thereclaimed product attains physical properties that allow it to be used,for example, as a building or construction material.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a process whereinsulfur is used for the disposal of matter, including but not limited toall toxic substances (including inorganic and organic toxic substances)and other hazardous substances, each of which have a boiling pointhigher than the temperature necessary to melt sulfur (solids andliquids) into a form that renders the matter non-toxic and additionallyreusable as a base material in granular or various molded forms. Thesulfur can be elemental sulfur, sulfur-based materials, sulfur-basedcompounds and sulfur-based substances.

It is another object of the present invention to provide a method forsolidifying toxic substances including, but not limited to,organochlorine compounds, such as PCBs, and heavy metals, and otherhazardous substances with sulfur, to prevent the toxic substances fromleaching out.

It is still another object of the present invention to provide a methodwherein a material solidified with sulfur, whose performance, such asphysical strength, and quality are high and constant, and from whichtoxic substances do not leach out, and, in addition, which may or maynot be molded or reused, can be industrially produced.

It is still further object of the present invention to provide a methodwherein material such as slag and/or dust resulting particularly frommetal processing such as steel-making, or the like, is mixed with amolten state sulfur and is solidified thereby. This method enablessolicification and, if necessary, the production of molded materials.

It is still another object of the present invention to provide a methodof manufacturing materials solidified with sulfur and, if necessary,molded, in which the performance, such as physical strength, and qualityare high and constant, and in which toxic substances such as harmfulheavy metals, PCBs, DDT, dioxins or the like will not leach out of thematerials.

It is still another object of the present invention to provide a methodfor producing molded materials solidified with sulfur, which method canprevent the molding operation environment from being adversely affectedby the generation of sulfurous acid gas, in spite of using melted sulfurwith materials such as slag and/or dust resulting particularly frommetal processing such as steel-making under high temperature.

It is still another object of the present invention to provide a methodwherein materials such as slag and/or dust resulting particularly frommetal processing such as steel making, can be cooled in either water,open air or other suitable means to form a granular form that can beused as is, or later melted and molded into various forms, for variousapplications.

One of the novel and unique characteristics of the present invention isthe discovery of liquid sulfur has the unique property of penetratingand encapsulating all substances that are soluble in sulfur at themolecular level, and the utilization of this discovery in the treatmentof organic and inorganic toxic substances by using liquid sulfur topenetrate and encapsulate the solid or liquid toxic substances at themolecular level.

Other and further objects, features, and advantages of the inventionwill appear more fully from the following description, taken inconnection with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a view illustrating an embodiment of an apparatus forsolidifying and sealing a toxic substance with sulfur, which apparatusis preferable in carrying out the method of the present invention.

FIG. 2 is a view illustrating another embodiment of the apparatus forsolidifying and sealing a toxic substance with sulfur.

DETAILED DESCRIPTION OF THE INVENTION

Although specific embodiments of the present invention will now bedescribed with reference to the drawings, it should be understood thatsuch embodiments are by way of example only and merely illustrative ofsome of the many possible specific embodiments which can representapplications of the principles of the present invention. Various changesand modifications obvious to one skilled in the art to which the presentinvention pertains are deemed to be within the spirit, scope andcontemplation of the present invention as further defined in theappended claims.

As the first embodiment, the present invention provides:

(1) A method for solidifying and sealing in a toxic substance withsulfur, comprising (A) heating and mixing a raw material mixturecontaining a substance to be treated and sulfur, at a temperature in therange of 119 to 159° C., to prepare a fluid mixed mixture under sulfurbeing melted, wherein the substance to be treated has a boiling point ofover 119° C. and has the solubility characteristics in a low-polarsolvent, the low-polar solvent being eluted earlier than t-butanol wheneluted from a silica gel column, and wherein the temperature is lowerthan the boiling point of the substance to be treated; and then (B)cooling the mixture, thereby solidifying and sealing in the substance tobe treated, and if necessary, molding the mixture into a prescribedshape;

(2) The method as stated in the above (1), wherein slag resultingparticularly from metal processing such as steel-making and/or dustresulting particularly from metal processing such as steel-making isheated and mixed together with the substance to be treated and sulfur;and

(3) The method as stated in the above (1), wherein the raw materialmixture contains an organochlorine compound and sulfur.

Preferable modes of the present invention can be mentioned:

(4) The method as stated in the above (1), wherein the water content ofthe substance to be treated is brought to less than 3% by weight, andthe substance to be treated is heated and mixed together with sulfur;and

(5) The method as stated in the above (2), wherein the water content ofeach of the slag resulting particularly from metal processing such assteel-making and/or the dust resulting particularly from metalprocessing such as steel-making is brought to less than 3% by weight,and the slag resulting particularly from metal processing such assteel-making and/or the dust resulting particularly from metalprocessing such as steel-making are heated and mixed together withsulfur and the substance to be treated whose water content is brought toless than 3% by weight.

According to the above first embodiment of the present invention, toxicorganochlorine compounds, such as PCBS, can be solidified and sealed inwith sulfur positively and quite effectively. Particularly, when slagand/or dust resulting particularly from metal processing such assteel-making is additionally used, a product solidified with sulfur thatis quite high in specific gravity and strength, and additionally thatmay be useful as a ballasting material, can be obtained.

Thus, according to the first embodiment of the present invention, a newmaterial can be obtained by solidifying and sealing in substances suchas organochlorine compounds that cannot be solidified effectively byconventional means. Therefore, the significance is quite remarkable inthe present invention in view of the prevention of environmentalpollution and, in addition, the reclamation and utilization ofresources.

Further, the inventors of the present invention found that, in additionto the harmful heavy metal species, substances having a boiling pointhigher than the temperature necessary to melt sulfur, can be solidifiedand sealed in with sulfur, according to the method of the presentinvention. Accordingly, as the second embodiment, the present inventionprovides a method for manufacturing materials solidified with sulfur,and a system of sealing in all toxic substances which have a boilingpoint higher than the temperature necessary to melt sulfur such asharmful heavy metal species, PCBs, DDT, dioxins, comprising the steps ofbringing the water content of a raw material to be mixed with sulfur,such as slag and/or dust resulting particularly from metal processingsuch as steel-making, to less than 3% by weight, heating and mixing themixture of raw materials including molten sulfur at a temperature in therange of from 119 to 159° C., to cause the melted sulfur to penetrateand encapsulate the raw material that is solid or liquid at themolecular level, thereby preparing a fluid mixed mixture, and thencooling the mixture. If necessary, the resultant cooled materialsolidified with sulfur can be molded into a desired shape during thecooling step, or it can be molded into a desired shape, or cooled into agranular form which can, if necessary, be remelted and molded into adesired shape.

Further, as the third embodiment, the present invention provides amethod for manufacturing materials solidified with sulfur, and a systemof sealing in harmful heavy metal species, comprising the steps ofbringing the water content of a raw material to be mixed with sulfur,such as slag and/or dust resulting particularly from metal processingsuch as steel-making, to less than 3% by weight, heating and mixing themixture of raw materials including molten sulfur at a temperature in therange of from 119 to 159° C., to cause the melted sulfur to penetrateand encapsulate the raw material that is solid or liquid at themolecular level, thereby preparing a fluid mixed mixture, and thencooling the mixture. If necessary, the resultant cooled materialsolidified with sulfur can be molded into a desired shape during thecooling step, or it can be molded into a desired shape, or cooled into agranular form which can, if necessary, be remelted and molded into adesired shape.

In particular, according to the second embodiment of the presentinvention, from waste materials containing all toxic substances whichhave a boiling point higher than the temperature necessary to meltsulfur such as harmful heavy metal species, PCBs, DDT, dioxins, amaterial solidified with sulfur from which the leaching out of the toxicsubstances such as harmful heavy metal species, PCBS, DDT, dioxins, iscompletely prevented, can be obtained. Additionally, the materialssolidified with sulfur having a high specific gravity and high physicalstrength can be useful as ballasting materials. The materials solidifiedwith sulfur can be used as a material to produce molded articles furtherprocessed.

According to the third embodiment of the present invention, a solidmaterial, such as slag and/or dust resulting particularly from metalprocessing such as steel-making, and dust from incinerated wastematerials, can be solidified and sealed in with sulfur quite effectivelyand positively, at the same time, by suppressing the occurrence ofsulfurous acid gas during heating to melt. In addition, a materialsolidified by sulfur that is high in physical strength can be obtained.

An apparatus for manufacturing materials solidified with sulfur, whichapparatus can be preferably used for carrying out the present invention,comprises a means for heating and drying a raw material to be mixed withsulfur, such as slag and/or dust resulting particularly from metalprocessing such as steel-making, a means for heating and mixing themixture of raw materials including molten sulfur, and, if necessary, ameans for molding a mixture of the solid material and the molten sulfurinto a desired shape or cooling it into a granular form. The apparatusfor manufacturing materials solidified with sulfur, which apparatus canbe used in the present invention, is effective to produce a molded itemsolidified with sulfur in a continuous manner.

Hereinbelow the present invention will be described in detail. Herein,“the present invention” denotes all of the above first, second, andthird embodiments, unless otherwise specified.

The method of the first embodiment of the present invention is describedfirst.

According to the first embodiment of the present invention, a compound(a substance to be treated) that is slightly soluble in water, hassolubility characteristics (solution-forming properties, solvability) ina low-polar solvent that has solubility characteristics in sulfur, anddoes not volatilize/spatter by heating and mixing with liquid sulfur,can be solidified and sealed in with sulfur.

In the first embodiment of the present invention, the term “low-polarsolvent” means a solvent that is eluted earlier than t-butanol when saidsolvent and t-butanol are eluted from a silica gel column. Examples ofthe low-polar solvents include, but are not limited to, for example,heptane, hexane, pentane, cyclohexane, trimethylpentane, carbondisulfide, carbon tetrachloride, trichloroethylene, xylene, toluene,benzene, chloroform, dichloromethane, and diisopropyl ether, which areenumerated in the order of elution, with the first eluted earliest.Whether or not a certain solvent is eluted earlier than t-butanol can beknown by comparing the elution time of the particular solvent with theelution time of t-butanol under the same conditions by using silica gelcolumn chromatography (elution analysis) employing, for example, silicagel as an adsorbent. In order to compare the elution times of theparticular solvent or t-butanol, the particular solvent and t-butanolmay be added to a silica gel column simultaneously. Alternatively,elution analysis of the particular solvent or t-butanol may be carriedout separately to compare the resulting elution times of these two. Inthe above elution of the particular solvent and t-butanol, another thirdsolvent or some other solvents may be used to control the elution rate.

In the first embodiment of the present invention, the substance to betreated may be heated and mixed with sulfur in the presence of asolvent, where the solvent is preferably a low-polar solvent. Forexample, the substance to be treated can be brought to a solution in thesolvent and then the resulting solution and sulfur are mixed, or thesolvent can be added to sulfur before or during the addition of thesubstance to be treated. The amount of the solvent to be used is notparticularly restricted, and it is preferably 0.01 to 100 weight parts,more preferably 0.1 to 10 weight parts, to 100 weight parts of sulfur.Alternatively, such a solvent can be omitted in carrying out the methodof the present invention, i.e. heating and mixing of the raw materialmixture can be carried out without the (low-polar) solvent.

By the term “a substance to be. treated that has solubilitycharacteristics in a low-polar solvent, which solvent is eluted earlierthan t-butanol when eluted from a silica gel column” is meant asubstance that is so-called soluble in the solvent. Herein, the term“being soluble” means that the solubility is generally 1,000 mg/l ormore (at 25° C.), preferably 2,000 mg/l or more (at 25° C.). In ordernot to allow the substance to be treated to volatilize/spatter whenheated together with liquid sulfur, the boiling point of the substancemust be higher than at least 119° C., and preferably it is higher than159° C. Herein, the term “a silica gel column” means a column filledwith a silica gel that is used for a column chromatography or athin-layer chromatography. As the silica gel, commercially available onesuch as Silica Gel 60 and Silica Gel 60G (trade names) can be used.Alternatively, an alumina gel column can be used instead of the silicagel column, when the solvent is more soluble in water.

In the first embodiment of the present invention, preferably thesubstance to be treated is one that is readily soluble in sulfur; thatis, it has a high solubility in the solvent that has a higher solubilityin sulfur when the solvent is dissolved in sulfur. Generally, thesolvent that is eluted much earlier when eluted from a silica gel columnis high in solubility in sulfur. More preferably, in the firstembodiment, the substance to be treated is a compound having theforgoing solubility characteristics in one solvent selected from amongheptane, hexane, pentane, cyclohexane, trimethylpentane, carbondisulfide, and carbon tetrachloride. Particularly preferably thesubstance to be treated is a compound that has the foregoing solubilitycharacteristics in hexane. Preferably, the substance to be treated isnot soluble in t-butanol. Herein, the term “not soluble in t-butanol”means that the substance does not have the foregoing solubilitycharacteristics in t-butanol. Preferably, the substance to be treated isslightly soluble in water. Herein, the term “slightly soluble” meansthat the solubility in water is generally 100 mg/l or less (at 25° C.).

t-Butanol can be mixed with water in arbitrarily-chosen proportions. Onthe other hand, the solvent (such as hexane and the like) that is elutedearlier than t-butanol in the elution analysis from a silica gel column,is a solvent that is hydrophobic; is not miscible with water andtherefore forms separate layers with it; has a low polarity; and is ableto dissolve sulfur. Therefore, the first embodiment of the presentinvention is characterized in that a compound (a substance to betreated) that is dissolved in sulfur can be solidified and sealed inwith sulfur, utilizing the fact that if the compound has solubilitycharacteristics in such a solvent low in polarity, the compound itselfresults in having solubility characteristics in sulfur according to themutual solubility characteristics among the compound, the solvent, andsulfur.

In the first embodiment of the present invention, a raw material mixturecontaining the substance to be treated and sulfur are heated and mixed.Herein the substance to be treated may be a simple substance of itself,a mixture of two or more of the substances, or a mixture of thesubstance to be treated with another substance, in which the form of thesubstance may be either a liquid or a solid. Examples of a raw materialcontaining such a substance to be treated include, for example,incineration ash, soot and dust, fly ash, waste PCBs from transformeroil, organochlorine compound-type insecticides, and extracts of theirresidue extracted from water or soil (polluted soil). Out of the solidraw materials, incineration ash generally does not contain water, butsometimes it contains water in an amount of about 5 to about 3% byweight, depending on its storage state.

In the first embodiment of the present invention, as a measure of thewater-insolubility of the compound; in other words, as a measure of theaffinity between the substance to be treated and sulfur, the solubilitycharacteristics in the low-polar solvent that is eluted earlier thant-butanol from a silica gel column is used. In addition to thesubstance's satisfying the solubility characteristics, preferably thesolvent strength parameter (ε⁰) of the solvent in which the substance tobe treated will be dissolved is in a prescribed range. Herein the term“solvent strength parameter (ε⁰)” means the solvent strength whenalumina is used as an adsorbent, and the solvent strength parameter hasthe relationship: ε⁰(silica)≈0.77×ε⁰(alumina) [L. R. Snyder, Advances inAnalytical Chemistry & Instrumentation, edited by C. R. Reilly, Wiley(1964)]. In the first embodiment, preferably the substance to be treatedis a compound having the foregoing solubility characteristics in asolvent that has a solvent strength parameter (ε⁰) of 0.5 or less (e.g.heptane (0.01, ε⁰ value, hereinafter the same being applied), hexane(0.01), cyclohexane (0.04), trimethylpentane (0.01), carbon disulfide(0.15), carbon tetrachloride (0.18), toluene (0.29), benzene (0.32),chloroform (0.40), dichloromethane (0.42), and diisopropyl ether(0.28)). The solvent strength parameter (ε⁰) is more preferably 0.2 orless, and particularly preferably 0.05 or less. In the first embodiment,that the solvent strength parameter (ε⁰) of a compound is 0.5 or lesscan be confirmed by the particular compound's having the aboveprescribed solubility characteristics in an organic solvent whosesolvent strength parameter (ε⁰) is known to be 0.5 or less. This isbased on the assumption that, when a compound is dissolved in a solvent,the compound has a solvent strength parameter at least equivalent tothat of the solvent. Thus, in the first embodiment, that the solventstrength parameter (ε⁰) is to be a prescribed value does not necessarilymean that the value of the solvent strength parameter (ε⁰) of thecompound is known; rather it means that the solvent strength parameter(ε⁰) measured by a conventional method or confirmed by the above methodsatisfies the prescribed conditions.

Further, in addition to the substance to be treated, to be solidifiedand sealed in with sulfur, having a prescribed solubilitycharacteristics in the solvent that is eluted earlier than t-butanol,preferably the substance to be treated has a dielectric constant (H.Wollmann et al., Pharmazie, 29, 708 (1974)) of 10 or less, and/or itsdipole moment (calculated in accordance with the Debye's formula andmeasured in benzene) is 1.5 or less. More preferably the dielectricconstant is 5 or less, and particularly preferably 3 or less. Further,more preferably the dipole moment is 1.3 or less, and particularlypreferably 0.

Examples of the substance to be treated that is the object to besolidified with sulfur in the method of the first embodiment include,for example, but are not limited to, organochlorine compounds, such aspolychlorinated biphenyls (PCBs), polychlorinated terphenyls (PCTs),polychlorinated quaterphenyls (PCQs), and dioxins includingpolychlorinated dibenzofurans (PCDFs) and polychlorinateddibenzoparadioxins (PCDDS) (e.g. dioxin), as well asp,p′-dichlorodiphenyltrichloroethane (DDT),p,p′-dichlorodiphenyldichloroethane (DDD), dieldrin,hexachlorocyclohexanes (HCHS) (benzenehexachlorides (BHCs)). Assubstances to be treated other than the above, for example,organophosphorus compounds, such as parathion, methyl parathion, EPN(O-ethyl O-p-nitrophenyl phenylphosphonothioate), and methyl demeton canbe mentioned.

In the method of the first embodiment, not only the toxic substance tobe treated itself but also other toxic substances that are contained inthe raw material containing the substance to be treated, can besolidified and sealed in satisfactorily with sulfur. Further, when anaggregate is used together with the above substance to be treated andsulfur, the resulting solidified product can be provided with furtherhigh physical strength. There are no particular restrictions on theaggregate, and as the aggregate, for example, slag, dust, and fine stonecan be used, with preference given to slag resulting particularly frommetal processing such as steel-making and/or dust resulting particularlyfrom metal processing such as steel-making. These materials such as slagand dust resulting particularly from metal processing such assteel-making are high in iron content and hence a high specific gravity,and therefore by using them, the resulting solidified product canadvantageously have a high specific gravity and excellent physicalstrength.

In the first embodiment of the present invention, the slag and dustresulting particularly from metal processing such as steel-making usedas aggregates can also be solidified and sealed in with sulfur, althoughsuch slag and dust or substances other than the substance to be treateddo not have the above specific solubility characteristics in thelow-polar solvent or sulfur. Namely, although slag and dust resultingparticularly from metal processing such as steel-making contain,generally, in addition to iron, toxic heavy metals, such as Pb and As,these heavy metal species are also sealed in with liquid sulfur, andafter the solidification and, if necessary, molding, the heavy metalspecies do not leach out from the solidified product.

In addition, in the method of the present invention, polluted soil,industrial waste, etc., and preferably, those that have been driedand/or incinerated to bring the water content to less than 3% by weight,can be used.

Sulfur in the liquefied state behaves like usual organic solvents. Thetemperature range in which sulfur is in the liquefied state is 119 to159° C., and sulfur turns to yellow fluid λ sulfur or brown viscous μsulfur, depending on the temperature. Sulfur is essentially of a colloiddispersion system, and it is known that sulfur is completely soluble inhexane and shows solubility characteristics in heptane, pentane,cyclohexane, carbon disulfide, etc. Further, the Clarke number of sulfuris 0.052 (the fifteenth in order of quantity from the largest), and theratio of sulfur present on the earth is large.

When sulfur is in the liquid state, the liquid sulfur can dissolvesubstances having low polarities, since the polarity of liquid sulfuritself is low. Further, when there are an organic solvent capable ofdissolving sulfur, and a compound capable of being dissolved in thatorganic solvent, sulfur also can be dissolved in the organic solventwith the compound dissolved in the organic solvent. Such a compound islow in polarity, like the above organic solvent, and insoluble in water,and the compound can be dissolved in sulfur even without the organicsolvent, since the compound has mutual solubility characteristics withsulfur. Utilizing this property, PCBs, whose outflow and pollution are asocial problem, can be heated and mixed together with sulfur to form auniform mixture. Then, by cooling the mixture to normal temperatures tosolidify the sulfur, the PCBs taken into the mixture-can be solidifiedand sealed in with sulfur. Further, surprisingly, the inventors of thepresent invention have found that, even when the thus-obtainedsolidified product is ground into a powder having a greater surfacearea, and the powder is dispersed into water and subjected to aleaching-out test, the PCBs taken into the solidified product do notleach out into water. Further, according to the method of the presentinvention, it seems that various other compounds having similarstructure and physical properties as those of PCBs, such asorganochlorine compounds including PCDFs, PCDDs (e.g. dioxin), and DDT,as well as other substances, can be solidified and sealed in.

The present invention (all of the above first, second and thirdembodiments) will be described based on the detailed embodiments shownin the respective figures.

Referring to FIG. 1, it shows a view illustrating an embodiment of theapparatus for solidifying and sealing in a toxic substance with sulfur,according to the present invention.

In FIG. 1, 1 indicates a hopper for a material such as slag resultingparticularly from metal processing such as steel-making; 2 indicates ahopper for a material such as incineration ash (this is the substance tobe treated or a raw material containing it in the first embodiment); 3indicates a hopper for a material such as dust resulting particularlyfrom metal processing such as steel-making; and 4, 5, and 6 indicatemetering tanks for the materials or aggregates (i.e., slag resultingparticularly from metal processing such as steel-making, incinerationash, and dust resulting particularly from metal processing such assteel-making, respectively) from the respective hoppers 1, 2, and 3. Inthe metering tanks, the materials or aggregates are metered, and themetered materials are fed to the feeder 7 (e.g. a movable meteringfeeder).

Further, 21, 22, and 23 indicate heating and drying apparatuses for thematerials and aggregates other than sulfur, which apparatuses areprovided with burners or the like, using fuel such as heavy oil. Theheating and drying apparatuses are of the type such as rotary kilns. Inthe heating and drying apparatuses, the materials and aggregates otherthan sulfur are heated to temperatures of the order of 120 to 200° C.,and their water contents are brought to generally less than 3% byweight, preferably less than 1.5% by weight, and more preferably lessthan 1% by weight.

In the Figures, additionally, 9, 10, and 11 indicate mixers, into whichthe material mixture, in a prescribed amount, is fed from the feeder 7;12 indicates a tank for sulfur as another material that will be chargedinto the feeder 7; and 13 indicates a tank for an additive. Sulfur isheated in the tank 12 to a prescribed temperature, and prescribedamounts of the sulfur are fed into the mixers 9, 10, and 11, throughpipes 14 and 15. The tank 12 may be provided with an apparatus fordeodorizing, if necessary. Further, an additive is appropriately fedthrough pipes 16 and 15. Herein, the additive can be one that serves todelay the solidification of sulfur.

After the mixture from the feeder 7, and the sulfur and the additivethrough the pipe 15 are charged into the mixers 9, 10, and 11, they aremixed (kneaded).

In reference to the mixers 9, 10, and 11, to select a type of mixer, itis suitable to select a mixer by placing importance on a time thatallows the molten sulfur to penetrate adequately into aggregates (slag,dust, etc., they act as if aggregates in concrete). Any type of mixercan be used, such as a single-screw mixer, a double-screw mixer, abatch-type mixer, and a continuous-type mixer, and generally is used adouble-screw pug mill-type circulation mixer of a batch type, whereintracks of paddle tips are overlapped to carry out uniform mixing. In themixers used in the present invention, it is required to adopt a systemthat allows molten sulfur to penetrate into aggregates satisfactorily bytaking as much time as is necessary.

However, in the case of the sulfur mixture in this invention, sulfur inthe mixed mixture is oxidized little, and mixing for a period as long asseveral minutes to several tens of minutes allows a compound and an atomto be solidified and sealed in sulfur in the molecular or atomic state.Further, it allows sulfur to penetrate into pore spaces on theaggregate, thereby enabling a good-quality sulfur mixture to beproduced.

Furthermore, if the mixer for the sulfur mixture is provided with aspeed-variable apparatus, such as an inventor, so that various types ofaggregates may be mixed, a good-quality sulfur mixture can be producedwith reduced wear of the mixer, reduced power consumption, and at lowcost.

More importantly, the materials in the mixer during the mixing must bekept generally at about 95 to about 150° C., and at not more than about160° C., and preferably at 115 to 140° C. Accordingly, it is preferableto jacket the outer circumference of the mixer an insulating materialand to heat the mixer wall by a heat source, such as an electric heater,a heating medium oil, or steam. Further, since it is needed to suck outdust and toxic substances such as harmful gases that are generated inthe mixer during the mixing when a toxic waste material is treated,sometimes the inside of the mixer is heated in order to prevent loweringof the temperature due to the suction.

It is suitable for the apparatus and the system of the present inventionthat the order of the feeding of the materials into the mixers can bearbitrarily changed. Thereby, a change in the type of material and achange in formulation can easily be coped with. Depending on the type ofmaterial and the formulation, in some cases, sulfur penetrates into theaggregate in a large amount during the mixing. In such a case, if therequired sulfur is fed into the mixer all at once, since the state inthe mixer becomes water-like and the mixture is apt to leak, forexample, from the sealed sections of the shaft and the discharge gate,or the mixture is sometimes splashed up by the mixing blades in themixer, the sulfur is preferably fed into the mixer in plural portionsdivided.

Since, in the sulfur mixture, use may be made of a material thatfacilitates abrasion, such as slag of iron and steel, preferably themixing blades and the case liner of the mixer should be made of anabrasion-resistant cast iron, a ceramic, etc.

In the present invention, the mixer is preferably of a batch type. Abatch-type mixer gives the advantage that dehydrated and heatedmaterials held in the insulated hoppers can be charged into the mixers,with changing the order of the charging in accordance with the purpose.

Various orders of charging can be selected; for example, (1) a methodwherein dust having fine-particles's particle diameters, the substanceto be treated such as waste materials (e.g. incineration ash), andsulfur are mixed, and thereafter coarse particles of slag and some otherwaste materials are charged, followed by mixing; (2) a method whereinfine particles of dust, coarse particles of slag, and the substance tobe treated are mixed and sulfur is charged into the mixture, followed bymixing, to complete the mixing; and (3) a method wherein the substanceto be treated, course particles, fine particles, and sulfur are chargedall at once, and mixing is then completed. Herein, the substance to betreated may be a toxic or hazardous substance, and may be omitted in theabove methods depending on the purpose, i.e. depending on the subjectsto be solidified and sealed in with sulfur.

The penetration of liquid sulfur into pore spaces on the solid materialscan be carried out by adjusting the temperature condition, stirringspeed, and residence time during mixing.

In the mixer used in the present invention, it is required that liquidsulfur diffuses, with the sulfur having affinity for all the surfacelayers of dehydrated and dried solids (preferably water content of lessthan 3% by weight). Therefore, it is important for the mixing time andthe temperature of the material to be kept within certain ranges. Thatis, since the physical properties of liquid sulfur are 11 cp and 7 cp at119 to 159° C., this temperature range must be kept. At 159° C. or over,the viscosity increases sharply, and at 187° C. it is 10⁵ cp, at whichthe sulfur is nearly an elastomeric material. At 119° C. it becomes asolid of a monoclinic system, and at 112° C. it becomes a solid of arhombic system. At normal temperatures, it becomes an Sα:S₈ cyclic solid(of a rhombic system), which is most stable, and when Sliq→Sα, due tothe affinity with heavy metals, such as Fe and Mn, their coexistence isbound to influence the stability and contraction property of Sα. Withrespect to the mixing time, if the mixing time is too short, theresulting solidification and sealing in may become insufficientsometimes causing the detectable leaching out of heavy metals, e.g. Pband Cd. The mixing time is preferably more than 10 min, more preferablymore than 15 min, and further preferably 20 min or more. In the presentinvention, it is important not merely to embed the raw materials but touniformly mix (knead) them with sulfur, to attain a complete sealing inof a toxic substance. With respect to the mixing pressure, it ispreferable to carry out the mixing in the present invention under normalpressure or under pressure (including a mechanical partial pressure inthe apparatus). According to the present invention, not only sulfur butalso organic compounds sealed in cannot be extracted with a solvent fromthe material solidified with sulfur. Contrary to the above, in aconventional method, the material or waste can be recovered from theembedded and consolidated product by dissolving the sulfur with asolvent (e.g. CS₂, S₂Cl₂).

In FIG. 1, 17 indicates a movable meter, and indicates a cooker vehicle.The fluid mixed mixtures prepared in the mixers 9, 10, and 11 aretransferred from the mixers, through the movable hopper 17 forsulfur-solidified material, to the cooker vehicle 18. In some cases, ifnecessary, the fluid mixture is discharged, to be poured into a mold tobe molded into a shape of a cylinder or a panel, for example, to form astake or a pile, in which shape, if necessary, reinforcement steel canbe placed in the molded material. In other cases, the fluid mixedmixture is discharged, to be molded and solidified into a desired shape.Alternatively, in order to obtain a material in a crushed or granularform to meet the purpose of application of the sulfur-solidifiedmaterial, an apparatus may be chosen in which a motor-driven sieve isplaced downstream of the path of the flow of the fluid mixture (at 140to 120° C.), to form particles with sizes in conformity with theopenings of the sieve, and the particles are plunged into water to besolidified (water-granulated). A movable heat-resistant belt conveyormay also be placed below the sieve, to allow particles with desiredsizes to be grouped, gradually cooled, and solidified, thereby producinggradually cooled and granular formed materials solidified with sulfur.

The case wherein the molding and cooling of the fluid mixture arecarried out by water granulation or gradual cooling is now describedfurther. According to water granulation, the fluid mixture having a hightemperature (140 to 120° C.) is abruptly cooled with water. This yieldsa water-granulated sulfur-solidified material which can be crushed, anda sulfur-solidified material, most of whose masses have sides 50 mm orbelow in size, can be obtained. The water-granulated sulfur-solidifiedmaterial is small in particle diameter and can be crushed further toabout sizes of sand grains, and the shapes of the obtained granules arenot uniform and resemble the shapes of crushed coke.

The physical strength of the masses of the sulfur-solidified materialobtained by water granulation is low, and therefore the masses can becrushed easily to smaller sizes, to be used as a fine aggregate(sand-like particles: 5 to 0.3 mm). Since the water-granulatedsulfur-solidified material is not uniform in particle diameter, and theouter surface of the granules is rugged, if the water-granulatedsulfur-solidified material is added to sand or gravel, the resultingmixture can be very easily made compact and is preferable, for example,as a high-load-bearing earth filling material for beaches.

On the other hand, according to gradual cooling, the solidified materialafter the cooling becomes single mass, which is high in specific gravityand high in physical strength. When the mass is crushed and the sizes ofthe particles are chosen, a coarse aggregate (40 to 5 mm) can beobtained. Since the gradually cooled sulfur-solidified material is highin physical strength and large in specific gravity, it can be used, forexample, as a filler in concrete caissons.

Further, when the sulfur-solidified material resulting fromwater-granulation or gradual-cooling as it is, or the granularly-formedor finely-crushed solidified material, is heated to from 120° C. to 140°C. (but not higher), it can be easily remelted and fluidized. Theremelted sulfur-solidified material can be easily molded into a desiredshape or cooled into a granular form; for example, into a plate or acylinder, such as a stake or a pile, by pouring it into a mold ofdesired shape. In this case, if the molded product is a large-sizedproduct small in surface area that is, for example, one obtained bygradual-cooling, since the heat conductivity is small, it is resistantto being remelted. Therefore, it is sometimes necessary to be made intoa finely crushed form as described above.

In the present invention, examples of materials that can be incorporatedinto the sulfur-solidified material include, for example, slag resultingparticularly from metal processing such as steel-making, dust resultingparticularly from metal processing such as steel-making, and wastematerials containing all inorganic or organic toxic substances whichhave a boiling point higher than the temperature necessary to meltsulfur (e.g. harmful substances, heavy metals, PCBs, DDT, dioxins), andparticulars thereof and compositions when they are processed aredescribed, for example, in JP-B (JP-B means examined Japanese patentpublication) Nos. 51440/1987, 15759/1986, 15274/1987, and 49680/1990.

There are no particular restrictions on the composition and the type(the origin) of slag resulting particularly from metal processing suchas steel-making and dust resulting particularly from metal processingsuch as steel-making for use in the present invention other than thematter above described. If the composition or the like of thesematerials is varied a little, stable solidification and sealing in canbe effected according to the present invention.

Slag resulting particularly from metal processing such as steel-makingmay be open-hearth furnace slag or convertor slag produced in theprocess of making steel by an open-hearth furnace or a convertor.Generally, slag resulting particularly from metal processing such assteel-making, for example, has the water content of 4 to 5% by weight.

Dust resulting particularly from metal processing such as steel-makingmay be a powder material that is collected in a dust collector in theprocess of making steel, for example, in a open-hearth furnace plant ora convertor plant. Although the major component of dust resultingparticularly from metal processing such as steel-making varies dependingon the formation conditions, it is mostly iron oxide, and the dustcontains toxic materials, such as Cr, Cu, As, Pb, and Zn. Generally,dust resulting particularly from metal processing such as steel-making,for example, has the water content of 4 to 10% by weight.

Examples of the compositions of slag resulting particularly from metalprocessing such as steel-making and dust resulting particularly frommetal processing such as steel-making that can be used in the presentinvention are shown in Tables 1 and 2, wherein “T-Fe” represents thetotal iron content of iron-containing components, such as Fe, Fe₂O₃, FeOand FeS, and the T-Fe is represented in terms of Fe₂O₃, and “M-Fe” meansa content of metal iron.

TABLE 1 Slag Resulting Particularly From Metal Processing Such AsSteel-Making T-Fe FeO SiO₂ CaO M-Fe A. 16.4% — 13.0% 44.0% 2.4% B. 58.8%12.4%  5.6% 24.3% — C. 24.6% — 12.8% 31.0% —

TABLE 2 Dust Resulting Particularly From Metal Processing Such AsSteel-Making T-Fe FeO SiO₂ CaO M-Fe A. 68.5% 69.5% 0.9% 2.9% 12.0% B.59.8% 14.8% 4.5% 3.8% — C. 61.9- 3.0- 1.2- 2.3- — 63.4% 4.8% 2.0% 3.8%

Additional examples of waste materials containing hazardous- ortoxic-substances, which can be used in the present invention, include,but are not limited to, waste materials containing toxic substances;soil contaminated with PCBs, DDT, dioxins, heavy metals or other toxicsubstances; dust (collected dust) released from metal-melting,refineries, and the like; dust (sludge) resulting from the treatment ofwaste water; dust or bottom ash resulting from incinerating residentialor commercial garbage; ground materials of defective electricapparatuses and appliances resulting from the production of electricapparatuses and appliances; ground materials of waste electricapparatuses and appliances (e.g. fluorescent lamps and batteries)retrieved from the market; and many other types of waste matter andtoxic substances. These can be used with other raw materials such as thesubstance to be treated and dust and/or slag resulting particularly frommetal processing such as steel-making, unless the objects of theinvention being affected. Further, the amount of these to be used may begenerally 5 to 95% by weight, preferably 5 to 10% by weight, in thetotal solid materials including other raw materials such as thesubstance to be treated and dust and/or slag resulting particularly frommetal processing such as steel-making.

Examples of the wastes are shown in the following table in detail, thetable also showing the species and amounts of toxic substances containedin the wastes.

TABLE (Unit: mg/kg) Waste¹⁾ Waste Soot electric Toxic Sludge SludgeSludge and apparatuses, Remarks: substances (A) (B) (C) dust appliancestest method²⁾ Alkyl 0.0025 0.0025 0.0059 0.005 0.0097 Notice No. 64;mercuries or less or less or less or less or less Attached Table No. 3Total 0.062 0.80 1.40 4.35 47.00 Notice No. 64; mercury or less or lessor less or less or less Attached Table No. 2 Cadmium or 350 510 6.50 1963.50 JIS K 0102 40.2 its compounds or less or less or less or less orless Lead and its 5.50 0.71 71.20 100000 120.00 JIS K 0102 39.2compounds or less or less or less or less or less Organo- 0 0.025 0.200.05 0.025 Notice No. 13; phosphorous or less or less or less or lessAttached Table No. 2 Hexavalent 0.025 0.25 0.70 192 0.05 JIS K 010251.2.1 chromium or less or less or less or less or less compoundsArsenic or 4.00 125 0.40 0.50 4.50 JIS K 0102 48.2 its compounds or lessor less or less or less or less Cyano- 0.25 0.13 0.50 0.10 0.25 JIS K0102 29.2 compounds or less or less or less or less or less Note: ¹⁾Thecontents of waste Sludge (A): Sludge generated when molded products wereglazed with ground slip of frit cadmium pigments. Sludge (B): Sludgegenerated by grinding spectacles blanks. Sludge (C): Neutralized sludgegenerated when waste gas in the production of sponge titanium waswashed. Soot and dust: Soot and dust obtained by collecting dustgenerated from a copper alloy casting furnace by a bag filter. Wasteelectric apparatuses and appliances: Glass waste (in a powdery form)obtained by crashing recovered lamps and defectives in fluorescent lampproduction steps. ²⁾“Notice” in the test method is an abbreviation of“Notice of the Environment Agency.”

The sulfur used as a material in the process of the present inventionneed not always be highly pure, and sulfur formed concomitantly in aprocess of desulfurization, for example, in plants that produce coke,make steel, or refine petroleum, and natural elemental sulfur, can servewell.

In the present invention, a material solidified with sulfur is composedof raw materials containing sulfur and the substance to be treatedhaving the prescribed boiling point (the first and second embodiments)and, if necessary, solubility in the low-polar solvent which is elutedearlier than t-butanol (the first embodiment). Further, the materialsolidified with sulfur may be composed of, in addition to sulfur and anobjective substance, a material selected from dust resultingparticularly from metal processing such as steel-making, slag resultingparticularly from metal processing such as steel-making, and other wastematerials. With respect to the physical properties of the materialsolidified with sulfur, the specific gravity varies depending largely onthe content of iron in the material aggregate. When the mixing ratio ofsulfur and dust and/or slag resulting particularly from metal processingsuch as steel-making is varied to obtain desired materials solidifiedwith sulfur, the relationship between the specific gravity of materialsand the total iron content of the obtained materials solidified withsulfur is shown in Table 3 below, by way of example.

The total iron content of the dust and/or slag resulting particularlyfrom metal processing such as steel-making out of the materials used inmaterials solidified with sulfur shown in Table 3 is mainly attributedto Fe₂O₃. For example, with regard to the total iron content (T—Fe) indust resulting particularly from metal processing such as steel-making,the T—Fe of open hearth furnace dust is 45 to 68.5%, and the T—Fe in ofconverter dust is 62 to 63%. On the other hand, for example, with regardto the T—Fe in slag resulting particularly from metal processing such assteel-making, the T—Fe of open hearth furnace slag is 16.5 to 59%, andthe T—Fe in converter slag is 24.6%, which T—Fe will vary depending onthe pretreatment method.

In dust and/or slag resulting particularly from metal processing such assteel-making, the particle distribution has a range, and dust resultingparticularly from metal processing such as steel-making has a maximumparticle distribution of 0.07 to 1 mm, while slag resulting particularlyfrom metal processing such as steel-making has a maximum particledistribution of 0.25 to 4 mm.

The physical strength of the material solidified with sulfur isinfluenced greatly by the width of the particle distribution of the usedaggregate. Therefore, regarding such aggregates as slag and/or dustresulting particularly from metal processing such as steel-making, anoptimum constitutional ratio ranging from fine particles to courseparticles is required for physical strength. Generally, by using anaggregate having a particle distribution in a larger particle diameterrange, a material solidified with sulfur excellent in physicalproperties such as uniaxial compressive strength can be obtained.Examples of constitutional ratios related to uniaxial compressivestrength are also shown in Table 3.

TABLE 3 Amount of raw material Particle Size to be used of the used(part by weight) raw material Dust Slag Dust Slag Uniaxial resultingfrom resulting from resulting from resulting from compressive Sulfersteel-making steel-making Specific T-Fe steel-making steel-makingstrength (1.98*¹) (1.82-5.2*¹) (2.04-5.2*¹) gravity (%) (mm) (mm)(kg/cm²) A1 2 1 5 2.69 26.41 0.07-0.1 0.25-1.0 174 (1.98*²) (2.72*²)(3.14*²) A2 2 1 5 2.69 26.41 0.07-0.1  2.0-3.5 306 (1.98*²) (2.72*²)(3.14*²) B1 1 2 2 3.36 37.29 0.07-0.1 0.25-1.0 347 (1.98*²) (3.86*²)(4.31*²) B2 1 2 2 3.36 37.29 0.07-0.1  2.0-3.5 478 (1.98*²) (3.86*²)(4.31*²) C1 1 2 3 4.06 48.91 0.07-0.1 0.25-1.0 512 (1.98*²) (5.09*²)(5.17*²) C2 1 2 3 4.06 48.91 0.07-0.1  2.0-3.5 650 (1.98*²) (5.09*²)(5.17*²) Note: *¹These values mean the range of specific gravity of eachraw material. *²These values mean specific gravity of the used rawmaterial.

Hereinafter, the ratio of sulfur to the raw material other than sulfurwill be described.

In the first embodiment of the present invention, the ratio of sulfur tothe substance to be treated in the raw material mixture is notparticularly restricted, and it may be in the range wherein thesubstance to be treated can be satisfactorily solidified and sealed inwith sulfur. Specifically, the weight ratio of sulfur to the substanceto be treated is preferably about (1:1×10⁻⁷) to (1:1×⁻³).

Particularly, when the substance to be treated is PCBs, the weight ratioof sulfur to PCBs is preferably (1:1×10⁻⁷) to (1:1×10⁻³), morepreferably (1:1×10⁻⁷) to (1:5×10⁻⁴) , and particularly preferably(1:1×10⁻⁶) to (1:1×10⁻⁴). On the other hand, when the substance to betreated is dioxins, the weight ratio of sulfur to dioxins is preferably(1:1×10⁻⁷) to (1:1×10⁻³) more preferably (1:1×10⁻⁶) to (1:5×10⁻⁴), andparticularly preferably (1:1×10⁻⁶) to (1:1×10⁻⁴).

In the first embodiment, the ratio of sulfur to the raw materialcontaining the substance to be treated such as incineration ash and flyash is not particularly restricted, and it may be in a range wherein thesubstance to be treated can be satisfactorily solidified and sealed inwith sulfur. The weight ratio of sulfur to the raw material other thansulfur containing the substance to be treated is preferably (0.5:9.5) to(8:2), more preferably (1:9) to (7:3), and particularly preferably(1.7:8.3) to (5:5).

In the first embodiment, if an aggregate, such as slag and/or dustresulting particularly from metal processing such as steel-making, isadditionally used, the ratio thereof is not particularly restricted, andit may be in the range wherein the substance to be treated can besatisfactorily solidified and sealed in with sulfur. Assuming the amountof sulfur to be 100 parts by weight, the amount to be used of the rawmaterial other than sulfur containing the substance to be treated ispreferably 2.5 to 1710 parts by weight, more preferably 4.3 to 810 partsby weight, and particularly preferably 10 to 440 parts by weight. On theother hand the amount to be used of an aggregate is preferably 1710 to2.5 parts by weight, more preferably 810 to 4.3 parts by weight, andparticularly preferably 440 to 10 parts by weight, for 100 parts byweight of sulfur.

In passing, in the first embodiment, when sulfur, the raw material otherthan sulfur containing the substance to be treated, slag resultingparticularly from metal processing such as steel-making, and dustresulting particularly from metal processing such as steel-making areused, their ratio is not particularly restricted, and it may be in arange wherein the substance to be treated can be satisfactorilysolidified and sealed in with sulfur. Assuming the amount of sulfur tobe 100 parts by weight, the amount to be used of the raw material otherthan sulfur containing the substance to be treated is preferably 2.5 to1710 parts by weight, more preferably 4.3 to 810 parts by weight, andparticularly preferably 10 to 440 parts by weight. Assuming the amountof sulfur to be 100 parts by weight, the amount to be used of slagresulting particularly from metal processing such as steel-making ispreferably 1700 to 0.025 parts by weight, more preferably 800 to 0.04parts by weight, and particularly preferably 435 to 0.1 parts by weight.On the other hand, assuming the amount of sulfur to be 100 parts byweight, the amount to be used of dust resulting particularly from metalprocessing such as steel-making is preferably 0.025 to 1700 parts byweight, more preferably 0.04 to 800 parts by weight, and particularlypreferably 0.1 to 435 parts by weight.

Parenthetically, in the case of using the raw material other than sulfurand containing the substance to be treated, the ratio of sulfur to thesubstance to be treated contained in the raw material is preferably inthe range as defined above.

In the second and third embodiments of the present invention, the mixingratio of sulfur with a material that is a solid or liquid state and isother than sulfur, such as slag and/or dust resulting particularly frommetal processing such as steel-making and some other toxic substances orthose containing toxic substances, is not particularly restricted aslong as it falls in a range wherein toxic substances in the materialother than sulfur are solidified and sealed in (encapsulated)satisfactorily with sulfur. The weight ratio of sulfur to the materialother than sulfur is preferably (3:1) to (1:8), more preferably (3:7) to(1:5), even more preferably (1:3) to (1:5), and particularly preferably(1:4) to (1:5). When the amount of the material other than sulfur issmall, that is, the amount of sulfur is rather a large amount, withinthe above-described range, all toxic substances which have a boilingpoint higher than the temperature necessary to melt sulfur (e.g. heavymetals, PCBs, DDT, dioxins, etc.) in the resulting solidified materialcan be more efficiently sealed in. It is also more easy to remelt andprocess the resulting solidified material. On the other hand, thesmaller the amount of sulfur to be used within the above-described rangeis, the higher the specific gravity and physical strength of theresulting solidified material will be.

Materials to be used to make the solidified material in the presentinvention are preferably, (1) sulfur and slag resulting particularlyfrom metal processing such as steel-making, and more preferably (2)sulfur, slag resulting particularly from metal processing such assteel-making and dust resulting particularly from metal processing suchas steel-making. The ratio of the used amount of these materials are; inthe case of (1), the amount of the slag resulting particularly frommetal processing such as steel-making to sulfur of 100 parts by weightis preferably 100 to 1,500 parts by weight, more preferably 200 to 800parts by weight, and particularly preferably 300 to 500 parts by weight;in the case of (2), the amount of the slag resulting particularly frommetal processing such as steel-making to sulfur of 100 parts by weightis preferably 50 to 1,500 parts by weight, more preferably 50 to 500parts by weight, and particularly preferably 100 to 300 parts by weight,and the amount of the dust resulting particularly from metal processingsuch as steel-making to sulfur of 100 parts by weight is preferably 30to 900 parts by weight, more preferably 60 to 650 parts by weight, andparticularly preferably 100 to 450 parts by weight. If slag resultingparticularly from metal processing such as steel-making and dustresulting particularly from metal processing such as steel-making areexcessive, the viscosity of the molten mixture may be lowered and thephysical strength of the solidified item may also be lowered. Further,in that case, the mixing and melting of the material, such as slagresulting particularly from metal processing such as steel-making, andsulfur may become unsatisfactory, sometimes resulting in failure to sealin toxic substances. If the amounts of slag resulting particularly frommetal processing such as steel-making and dust resulting particularlyfrom metal processing such as steel-making are too small, the specificgravity of the solidified item may be decreased and the physicalstrength thereof may be lowered.

Furthermore, in the present invention, into the aggregate (solid rawmaterial) to be mixed with molten sulfur, may be added shredder dust, inan amount that does not impair the properties of the sulfur-solidifiedmaterial; for example, in an amount of about 55% by weight or below, andpreferably 30% by weight or below, based on the aggregate. The term“shredder dust” means dust formed when waste automobiles or the like arecrushed finely by a crusher for final disposal treatment, and shredderdust may take various forms, such as the forms of grinds and powderydust. Components of shredder dust include, for example, resins, rubbers,fibers, foamed urethane, iron, mercury, lead, and paints, andparticularly heavy metals. The materials contained in shredder dustpresent a problem with respect to waste material treatment.

Further, materials to be used other than sulfur; such as slag resultingparticularly from metal processing such as steel-making, dust resultingparticularly from metal processing such as steel-making, EP dust (thatis, dust collected from electrostatic precipitator), andharmful-heavy-metal-containing sludge dried material (e.g. titaniumwaste slag), which materials contain a fine powder, are slashed in alldirections in the practical processing step, in some cases. Since thesecontain toxic substances such as harmful heavy metals, it is required toprovide an apparatus for removing the generation of secondary pollution.In this case, as shown in FIG. 2, three-step processing can be used, insuch a manner that, after the material 50 is dried by a dryer 51, dustis removed by a cyclone 52; fine powder is removed by a bag filter 53;and finally a wet-type scrubber 54 is used for the purpose ofdeodorization and dust removal.

In the figure, section 55 within the broken-line is provided withjuxtaposed rows, or three rows, in conformity with the purpose ofapplication, i.e. for slag, dust, and waste materials (these may besubstances to be treated).

In the figure, 56 indicates a hopper, 57 indicates a metering tank, and58 indicates a mixer. In the figure, the same reference numeralsindicate the same members as described in FIG. 1.

The present invention is now described in more detail based on thefollowing examples, but, of course, the present invention is not limitedto these examples.

EXAMPLES Example 1

A. Solidification with Sulfur

By using the following materials, materials solidified with sulfur wereproduced.

(1) Slag Resulting from Steel-making

500 g of so-called converter slag was prepared.

Particle diameter: 4.0 to 0.25 mm gradually cooled slag (ID-C3)

Water content: shown below

Bulk specific gravity: 2.04 g/cm²

T—Fe: 58.8%

(2) Dust Resulting from Steel-making

400 g was prepared.

Particle diameter: 1.0 to 0.25 mm magnetically separated powder (LD-OB)

Water content: shown below

Bulk specific gravity: 1.82 g/cm²

T—Fe: 59.8%

(3) Sulfur

In this particular example, sulfur obtained in desulfurization inrefining of petroleum, which sulfur had a purity of 99.5% or over, wasused, in an amount of 400 g. Naturally, this type of sulfur was freefrom moisture. Generally this sulfur is stored in a liquefied state byheating it to 120±5° C.

Before mixing and melting the sulfur, the water content of the slagresulting from steel-making and the dust resulting from steel-making wasbrought to less than 1% by weight, less than 3% by weight, about 7% byweight, or about 10% by weight, respectively, based on the total amount,and they were mixed. The three components were added approximatelysimultaneously and were mixed at 120 to 130° C. for 20 min, using adouble-screw pug mill-type circulation kneader. The thus obtained molded(gradually cooled) materials were tested with respect to leaching out ofheavy metals and physical strength, according to the following methods.Further, the specific gravity of the thus obtained molded materials wasmeasured.

B. Testing Method

(1) Test Method for Leaching Out of Heavy Metals

Each of the obtained molded materials solidified with sulfur was groundto particles, and the obtained particles were passed through a sieve tocollect the particles having particle diameter of 0.5 to 5 mm, toprepare Sample. The thus prepared Sample was brought into pure waterwhich had its pH value adjusted to 5.8 or higher but 6.3 or below, sothat the content of Sample became 10% (w/v) and the total amount of themixture of Sample in water was made to at least 500 ml. This mixture wasstirred at 20° C by using a stirrer, the width of stirring being 4 cm ormore but 5 cm or less at stirring speed of 200 times/min. for 6 hours,thereby to carry out leaching out of heavy metals from the moldedmaterial solidified with sulfur into water. The resulting liquid wasfiltered through a filter having a pore diameter of 1 μm, to prepareTest liquid. Leaching out of each heavy metal in the Test liquid wasmeasured according to the method described in the notification No. 13from the Environment Agency, such as the atomic absorption spectrometryshown in JIS K 0102.

With respect to the degree of pollution for the criteria for soilenvironment, the measurement was carried out according to the methoddescribed in the notification No. 46 from the Environment Agency, byusing Sample prepared in the same manner as described above except thatthe particle diameter of Sample was made 2 mm or less.

(2) Test Method for Physical Strength

As a scale of physical strength of Sample, uniaxial compressive strengthof each sample prepared in the above (1) was measured according to JIS A1108. The results are shown in Table 4.

TABLE 4 Experiment No. 1 2 3 4 Water content less than less than about7% about 10% (wt. %) 1% 3% State at the Mixing and melting During themixing time of mixing could be done with and melting, foaming littleabnormality occurred within the mixture Generated gas During the mixingand During the mixing melting, there was and melting, an littlegeneration of irritating odor due an irritating odor to the smell ofsulfur dioxide gas was remarkably generated, and therefore a deodori-zing apparatus was required to be installed Leaching out Leaching out ofheavy Leaching out of hea- of heavy metals from the vy metals from themetals* material solidified material solidified by sulfur into water bysulfur become was little much and components in amounts exceeding thecriteria for waste leached out At or At or Some components of below thebelow the Zn, As, Pb, etc. criteria criteria exceeded the for soil forleach- criteria for leach- environ- ing of ing out of harmful mentharmful heavy metals heavy met- als, etc. Hg <0.0005 Hg <0.005 Hg 0.005to 0.01 mg/l mg/l mg/l Pb <0.01 Pb <0.3 Pb 0.3 to 0.5 mg/l mg/l mg/l As<0.01 As <0.3 As 0.3 to 0.5 mg/l mg/l mg/l Uniaxial 300 kg/cm² 280kg/cm² 200 kg/cm² 180 kg/cm² compressive strength Specific 3.51 3.282.34 2.11 gravity Note: *Leaching-out amounts of heavy metals from theraw materials before solidifying with sulfur are Hg 0.005 mg/l; Pb 3.0mg/l; and As 1.0 mg/l. “<” means much smaller than the amount, e.g.<0.0005 mg/l means that it was much smaller than 0.0005 mg/l.

In Experiment Nos. 1 and 2, a rise in viscosity under melting conditionduring mixing occurred remarkably, whereas in, Experiment Nos. 3 and 4,a rise in viscosity under melting condition did not occur due to thewater content.

When three components, i.e. dust and slag resulting from steel-making,and sulfur, were mixed, with the water content before the mixing andmelting being over 3%, it happened that steam and sulfurous acid gaswere generated by heating at a temperature higher than 120° C., and theinner pore spaces in the mixed material were greatly increased, whichseemed to result in lower physical strength. As a result, in such asystem wherein water remained significantly in the solid raw material,the penetration of liquid sulfur into the solid phase becameunsatisfactory. When the molded material solidified with sulfur wasbroken and the broken materials were shaken in water, by the method ofjudging the suppression of leaching out of toxic heavy metals, it wasrecognized that toxic heavy metals leached out.

As is apparent from the results shown in Table 4, if the water contentat the time of mixing and melting exceeds 3%, an irritating odor due tothe smell of sulfurous acid gas became strong, the uniaxial compressivestrength of the material solidified with sulfur was under the sameconditions, the leaching out of heavy metals could not be prevented, andtherefore it can be understood that it is important to control theinitial water content.

Example 2

Molded materials were manufactured in the same manner as Experiment No.1 in Example 1, except that raw materials or their composition werechanged as shown in Table 5 below. Physical properties of the moldedmaterials were measured in the same manner as in Example 1. The resultsare shown in Table 5.

TABLE 5 Amount of raw material to be used (part by weight) Dust SlagExperi- resulting resulting Uniaxial ment from from Fly Specificcompressive No. Sulfur steel-making steel-making Gravel Macadam ash*¹gravity strength   5*² 1 2 3 — — — 4.06 650 kg/cm² 6 1 — — 2 3 — 2.50128 kg/cm² 7 1 — — — — 5 2.31  68 kg/cm² 8 1 — 5 — — — 2.12  27 kg/cm²Note: *¹The fly ash used had a water content of less than 3%. *²InExperiment No. 5, the raw materials and composition were the same asthose described in column C2 in Table 3.

Example 3

Materials

The sulfur, slag resulting from steel-making, and dust resulting fromsteel-making used in Example 3 (as well as in the following examples),were prepared in the same manner as in Example 1.

PCB Reagents

The PCB reagents used in the example were four commercially availablePCB standard substances: Kanechlor KC-300, KC-400, KC-500, and KC-600(trade names), manufactured by G.L. Science Co., which were different inthe degree of chlorination.

Type of PCB reagent Trade name Concentration (g/ml) Kanechlor KC-300651.0 Kanechlor KC-400 603.5 Kanechlor KC-500 534.0 Kanechlor KC-600594.0

PCBs are soluble in hexane (the solubility at ordinary temperature isabout 200 mg/l or more) but are slightly soluble in water. Thesolubility of PCBs in water at 25° C. is about 0.3 mg/l (assuming PCBsas a mixture of PCBs each having 3 to 6 chlorine atoms), and when PCBshave smaller number of chlorine atoms, the solubility is about 1 mg/l.PCBs have a boiling range of about 325 to about 420° C. (760 mmHg),which range may vary due to the number of chlorine atoms (3 to 6chlorine atoms) in the PCB mixture.

To a mixture having the mixing ratio of 900 g of slag resulting fromsteel-making and 600 g of dust resulting from steel-making, each ofwhich was a dehydrated solid having a water content of less than 3% byweight, and 555 g of sulfur (2,055 g in all), was added a hexanesolution (50 ml) containing a PCB mixture (Kanechlor KC-300 3.84 ml,Kanechlor KC-400 4.14 ml, Kanechlor KC-500 4.68 ml, and Kanechlor KC-6004.21 ml; totaling about 10 mg in terms of PCBs); the mixture was stirredand heated to evaporate the hexane, and after the stirring was continuedto sufficiently mix for about 15 min or more at a temperature of 135 to145° C., the mixture was plunged into water, to form a water-granulatedsolid (slag). The water-granulated slag had a specific gravity of 3.2g/cm³ and a monoaxial compression strength of 460 kg/cm².

As a leaching-out test for the leaching-out of PCBs from thewater-granulated slag, an assay was made for a measurement certificate(method of measurement: JIS K 0093) in accordance with Notice No. 13 ofthe Environment Agency, and the assay showed a leached-out amount lessthan the detection limit value of 0.0005 mg/l, and it was judged thatPCBs were not detected.

Example 4

900 g of slag resulting from steel-making, which was a dehydrated solidhaving an water content of less than 3% by weight, 600 g of dustresulting from steel-making, which was a dehydrated solid having anwater content of less than 3% by weight, and 660 g of sulfur (totalingto 2,160 g) were mixed and were made into a product solidified withsulfur by water granulation.

Separately, a hexane solution (50 ml) of a PCB mixture (Kanechlor KC-3000.39 ml, Kanechlor KC-400 0.41 ml, Kanechlor KC-500 0.047 ml, andKanechlor KC-600 0.42 ml) was prepared, wherein the amount of PCBs wasabout 1 mg.

This hexane solution of a PCB mixture was added to the above productsolidified with sulfur (water-granulated product), and the resultingmixture was heated to 60 to 80° C., to evaporate the hexane. Then, themixture was heated to 130 to 140° C., to be brought to a melted state,and after mixing for about 10 min, it was allowed to stand to cool andsolidify at room temperature. This was used as a sample. This sample(gradually-cooled solidified product) had a specific gravity of 3.1g/cm³ and a monoaxial compression strength of 440 kg/cm².

Next, the sample was ground until all particles of the sample passedthrough a 2-mm sieve. The sample passed through the sieve was added topure water (having a pH of 5.8 to 6.8), whose amount was ten times thatof the sample, thereby preparing a sample liquid.

The sample liquid was shaken as follows: the number of shakes, 200 permin; the width of the shakes, 4 cm or more but 5 cm or below; and thetime of the shaking, 6 hours.

After the thus shaken sample liquid was allowed to stand for about 10 to30 min, the supernatant liquid was centrifuged at about 3,000 rpm for 20min, and the resulting supernatant liquid was passed through a 0.45-μmmembrane filter, to obtain an analyte liquid.

The thus obtained analyte liquid was subjected to the leaching-out testfor PCBs.

The result of the leaching-out test showed a leached-out amount lessthan 0.0005 mg/l (less than the detection limit).

Example 5

1500 g of slag resulting from steel-making, and 500 g of dust resultingfrom steel-making, each of which was a dehydrated solid having a watercontent of less than 3% by weight, and 410 g of sulfur were mixed andwere made into a product solidified with sulfur by water granulation. Ahexane solution (50 ml) of a PCB mixture (Kanechlor KC-300, KanechlorKC-400, Kanechlor KC-500, and Kanechlor KC-600, 5 ml of each, totaling20 ml i.e. about 11.9mg in total amounts of PCBs) separately preparedwas added to the above product solidified with sulfur (water-granulatedproduct), and the resulting mixture was heated to 60 to 80° C., toevaporate the hexane. Then, the mixture was heated to 130 to 140° C., tobe brought to a melted state, and after mixing for about 10 min, it wasallowed to stand to cool and solidify at room temperature, to obtain asample. This sample (gradually-cooled solidified product) had a specificgravity of 3.2 g/cm³ and a monoaxial compression strength of 640 kg/cm².The sample was processed and subjected to the leaching-out test in thesame manner as in Example 4. The result of the leaching-out test showeda leached-out amount less than 0.0005 mg/l (less than the detectionlimit).

Example 6

A hexane solution (50 ml) of a PCB mixture (Kanechlor KC-300, KanechlorKC-400, Kanechlor KC-500, and Kanechlor KC-600, 5 ml of each, totaling20 ml, i.e. about 11.9 mg in terms of PCBS) was added to 500 g ofsulfur. The mixture was heated to 60 to 80° C., to evaporate the hexane.Then the mixture was heated to 130 to 140° C., to be brought to a meltedstate, and after mixing for about 10 min, it was allowed to stand tocool and solidify at room temperature, to obtain a sample. This sample(gradually-cooled solidified product) had a specific gravity of 1.9g/cm³ and a monoaxial compression strength of 20 kg/cm². This sample wastreated and subjected to the leaching-out test in the same manner as inExample 4.

The result of the leaching-out test showed a leached-out amount lessthan 0.0005 mg/l (less than the detection limit).

Example 7

A sample was obtained in the same manner as in Example 5, except that ahexane solution (50 ml) of a PCB mixture (Kanechlor KC-300, KanechlorKC-400, Kanechlor KC-500, and Kanechlor KC-600, 10 ml of each, totaling40 ml, i.e. about 23.7 mg in terms of PCBs) was added to 500 g ofsulfur. This sample (gradually-cooled solidified product) had a specificgravity of 1.9 g/cm³ and a monoaxial compression strength of 20 kg/cm².This sample was treated and subjected to the leaching-out test in thesame manner as in Example 5, and the result showed a leached-out amountless than 0.0005 mg/l or less (less than the detection limit).

Comparative Example 1

300 g of slag resulting from steel-making and 200 g of dust resultingfrom steel-making were mixed, heated, and dried, to obtain a powderhaving a water content less than 3% by weight, and a hexane solution (50ml) of a PCB mixture (Kanechlor KC-300, Kanechlor KC-400, KanechlorKC-500, and Kanechlor KC-600, 5 ml of each, totaling 20 ml, i.e. about11.9 mg in terms of PCBS) was added to the powder. The mixture washeated to 60 to 80° C., to evaporate the hexane. Then the mixture washeated to 130° C., and after stirring for 10 min, it was allowed tostand to cool and solidify at room temperature, to obtain a sample. Thissample (powder product) had a specific gravity of 2.2 g/cm³. This samplewas treated and subjected to the leaching-out test in the same manner asin Example 4. The result of the leaching-out test showed a leached-outamount of less than 0.0005 mg/l (less than the detection limit).

Comparative Example 2

300 g of slag resulting from steel-making and 200 g of dust resultingfrom steel-making were mixed, heated, and dried, to obtain a powderhaving a water content of less than 3% by weight, and a hexane solution(50 ml) of a PCB mixture (Kanechlor KC-300, Kanechlor KC-400, KanechlorKC-500, and Kanechlor KC-600, 10 ml of each, totaling 40 ml, i.e. about23.7 mg in terms of PCBS) was added to the powder. Thereafter themixture was treated in the same manner as in Comparative Example 1, toobtain a sample. This sample (garadually-cooled powder product) had aspecific gravity of 2.2 g/cm³. This sample was treated and subjected tothe leaching-out test in the same manner as in Comparative Example 1,and the result showed a detection of PCBs with a leached-out amount of0.003 mg/l (the detection limit being 0.0005 mg/l).

From the above results, it can be seen that, in the solidified materialsobtained by using sulfur, slag resulting from steel-making, and dustresulting from steel-making in accordance with the method of the presentinvention, PCBs were completely solidified and sealed in (Examples 3, 4and 5). It can be understood that, similarly in the solidified productsobtained by using sulfur in accordance with the method of the presentinvention, PCBs were completely solidified and sealed in (Examples 6 and7). In contrast, in the cases in which slag resulting from steel-makingand dust resulting from steel-making were used without using sulfur,solidification and sealing in were possible if the amount of added PCBswas small (Comparative Example 1), but PCBs were not sealed in and theyleached out if the amount of added PCBs was increased (ComparativeExample 2). From Comparative Examples 1 and 2, it can be understood thatPCBs can be sealed in with using slag and dust resulting fromsteel-making that can be used as subsidiary materials in the method ofthe present invention by taking them into pores of the slag and dustresulting from steel-making even if sulfur is not used, but if theamount of PCBs is increased, PCBs cannot be sealed in, resulting in theleaching-out thereof.

Example 8

900 g of slag resulting from steel-making, which is a dehydrated solidhaving a water content of less than 3% by weight, 600 g of dustresulting from steel-making, which is a dehydrated solid having a watercontent of less than 3% by weight, and 660 g of sulfur (2,160 g in all)are mixed and are water-granulated, to produce a material solidifiedwith sulfur.

Separately, a toluene solution of 1 mg of a dioxin standard substance(as an equivalence (TEQ) to 2,3,7,8,-T₄CDD) is prepared.

This dioxin toluene solution is added to the above sulfur-solidifiedmaterial (water-granulated product), and the mixture is heated to 100 to115° C., to evaporate the toluene. Further, the mixture is heated to 130to 140° C., to be brought to a melted state, and after mixing for about10 min, the melted mixture is allowed to stand to cool and solidify atroom temperature. The resulting product is used as a sample. Thereafterthe sample is treated in the same manner as in Example 4 and issubjected to a dioxin leaching-out test.

By the leaching-out test, dioxins are not detected.

Example 9

A toluene solution (50 ml) of 10 mg of dioxins is added to 500 g ofsulfur. Then, the mixture is heated to 100 to 115° C., to evaporate thetoluene, and then it is heated to 130 to 140° C., to be brought to amelted state, and after mixing for about 10 min, the mixture is allowedto stand to cool and solidify at room temperature, to obtain a sample.Thereafter the sample is treated in the same manner as in Example 8 andis subjected to the dioxin leaching-out test.

As a result of the leaching-out test, the leached-out amount is lessthan the detection limit.

Comparative Example 3

From 900 g of slag resulting from steel-making and 600 g of dustresulting from steel-making, each of which was a dehydrated solid havinga water content of less than 3% by weight, and 660 g of sulfur (2,160 gin all), a material solidified with sulfur was produced bywater-granulating in the same manner as in Example 3.

Separately, a hexane (100 ml) dispersion solution of 10 mg of diethyleneglycol was prepared.

This hexane dispersion solution of diethylene glycol was added to theabove sulfur-solidified material (water-granulated product), and themixture was heated to 60 to 80° C., to evaporate the hexane. Further,the mixture was heated to 130 to 140° C., to be brought to a meltedstate, and after mixing for about 10 min, the melted mixture was allowedto stand to cool and solidify at room temperature. The resulting productwas used as a sample. Thereafter the sample was treated in the samemanner as in Example 3 and was subjected to a leaching-out test fordiethylene glycol.

As a result of the leaching-out test, 3 mg/l of diethylene glycol wasdetected.

Herein, diethylene glycol is not soluble in the low-polar solvents, suchas benzene, toluene, carbon tetrachloride and chloroform; but it hassolubility characteristics in and is miscible arbitrarily with solvents(not low in polarity), such as water, alcohols, ethers and acetone. Theboiling point of diethylene glycol is 245° C. (133° C./14 mmHg).

In another embodiment, the present invention is a method formanufacturing materials solidified with sulfur, and a system of sealingin all toxic substances which have a boiling point higher than thetemperature necessary to melt sulfur such as harmful heavy metalspecies, PCBs, DDT, dioxins, comprising providing a raw material to bemixed with the sulfur, reducing the water content of the raw material,such as slag resulting particularly from metal processing such assteel-making and/or dust resulting particularly from metal processingsuch as steel-making, to approximately less than 3% by weight, mixingthe material with the sulfur to produce a mixture of materials, heatingthe mixture of raw materials including molten sulfur at a temperature inthe range of approximately 119 to 159° C., to cause the melted sulfur topenetrate into apertures on the raw material that is solid or to causethe melted sulfur to mix with and seal the raw material that is liquid,and then, if necessary, molding the mixture of raw materials into ashape or cooled into a granular form.

In another further embodiment, an apparatus for manufacturing materialssolidified with sulfur, which apparatus is preferable to carry out thepresent invention, comprises a heating and drying device for reducingthe water content of a raw material to be mixed with the sulfur, such asslag resulting particularly from metal processing such as steel-makingand/or dust resulting particularly from metal processing such assteel-making, a means for heating and mixing the mixture of rawmaterials including molten sulfur, and, if necessary, a means formolding the mixture of materials into a shape or cooled into a granularform.

According to the present invention, a solid or liquid material, such asslag resulting particularly from metal processing such as steel-making,and/or dust resulting particularly from metal processing such assteel-making and dust from incinerated waste materials, can besolidified and sealed in with sulfur quite effectively and positively,at the same time, by suppressing the occurrence of sulfurous acid gasduring heating to melt, and a material solidified with sulfur that ishigh in physical strength can be obtained. In particular, according tothe present invention, from waste materials containing toxic substancessuch as harmful heavy metal species, PCBs, DDT, dioxins, a materialsolidified with sulfur from which the leaching out of toxic substancessuch as harmful heavy metals species, PCBs, DDT and dioxins, iscompletely prevented, can be obtained. Additionally, the materialssolidified with sulfur which have a high specific gravity and a highphysical strength can be useful as ballasting materials. The materialssolidified with sulfur can be used as a raw material to produce moldedarticles further processed.

The apparatus for manufacturing materials for use in the presentinvention to produce an item solidified with sulfur can be made to runin a continuous manner. Alternatively, in order to obtain a material ina granular form, to meet the purpose of application of thesulfur-solidified material, an apparatus may be chosen in which amotor-driven sieve is placed downstream of the path of the flow of thefluid mixture (at 120 to 140° C.), to form particles with sizes inconformity with the openings of the sieve, and the particles are plungedinto water to be solidified (water-granulated). A movable heat-resistantbelt conveyor may also be placed below the sieve, to allow particleswith desired sizes to be grouped, gradually cooled, and solidified,thereby producing gradually-cooled and granular-formed materialssolidified with sulfur.

According to water granulation, the fluid mixture having a hightemperature (120 to 140° C.) is abruptly cooled with water which can becrushed, and a sulfur-solidified material, most of whose masses havesides 50 mm or below in size, is obtained. The water-granulatedsulfur-solidified material is small in particle diameter and can becrushed further to about sizes of sand grains, and the shapes of theobtained granules are not uniform and resemble the shapes of crushedcoke. The physical strength of the masses of the sulfur-solidifiedmaterial obtained by water granulation is low, and therefore the massescan be crushed easily to smaller sizes, to be used as a fine aggregate(sand-like particles: 0.3 to 5 mm). Since the water-granulatedsulfur-solidified material is not uniform in particle diameter, and theouter surface of the granules is rugged, if the water-granulatedsulfur-solidified material is added to sand or gravel, the resultingmixture can be very easily made compact and is preferable, for example,as a high-load-bearing earth filling material for beaches.

On the other hand, according to gradual cooling, the solidified materialafter the cooling becomes a single mass, which has a high specificgravity and a high physical strength. When the mass is crushed and thesizes of the particles are chosen, a coarse aggregate (5 to 40 mm) canbe obtained. Since the gradually-cooled sulfur-solidified material has ahigh physical strength and a large specific gravity, it can be used, forexample, as a filler in concrete caissons.

When the sulfur-solidified material resulting from water-granulation orgradual-cooling as it is, or the granularly-formed or finely-crushedsolidified material, is heated to 120° C. to 140° C. (but not higher),it can be easily remelted and fluidized. The remelted sulfur-solidifiedmaterial can be easily molded into a shape; for example, into a plate ora cylinder, such as a stake or a pile, by pouring it into a mold. Inthis case, if the product is a large-sized product small in surfacearea, that is, for example, one obtained by gradual-cooling, since theheat conductivity is small, it is resistant to being remelted.Therefore, it is sometimes necessary to be made into a finely crushedform as described above.

Additional examples of waste materials containing hazardous- ortoxic-substances, which can be used in the present invention, includewaste materials containing toxic substances; soil contaminated withPCBs, DDT, dioxins, heavy metals and other toxic substances; dust(collected dust) released from metal-melting, refineries, and the like;dust (sludge) resulting from the treatment of waste water; dust orbottom ash resulting from incinerating residential or commercialgarbage; ground materials of defective electric apparatuses andappliances resulting from the production of electric apparatuses andappliances; ground materials of waste electric apparatuses andappliances (e.g. fluorescent lamps and batteries) retrieved from themarket; and many other types of waste materials and toxic substances,including all solid or liquid forms of inorganic or organic toxicsubstances. The inorganic toxic substances include the atomic ormolecular substances and matters containing these substances. These canbe used with other raw materials such as the substance to be treated anddust and/or slag resulting particularly from metal processing such assteel-making, unless the objects of the invention are affected. Further,the amount of these to be used may be generally 5 to 95% by weight inthe total solid raw materials including other raw materials such as thesubstance to be treated and dust and/or slag resulting particularly frommetal processing such as steel-making.

The sulfur used as a material in the process of the present inventionneed not always be highly pure, and sulfur formed concomitantly in aprocess of desulfurization, for example, in plants that produce coke,make steel, or refine petroleum, and natural elemental sulfur, can servewell.

In still a further embodiment, the present invention relates to aprocess for safe disposal of matter, including, but not limited to, alltoxic substances and other hazardous substances, each of which (i) havea boiling point higher than the temperature necessary to melt sulfur and(ii) the solubility characteristics in a low-polar solvent that elutesearlier than t-butanol when eluted from a silica gel column, into a formthat renders the matter: (1) non-toxic, in the case of a toxicsubstance, in that the leaching thereof is eliminated, and in some cases(2), in addition to the above (1), reusable as a base material ingranular or various molded forms. The process includes using sulfur forthe disposal, encapsulation, containment, processing, treating,destruction and immobilizing, and if necessary recycling, of wastematerials and all toxic substances which have (i) a boiling point higherthan the temperature necessary to melt sulfur and (ii) the solubilitycharacteristics in a low-polar solvent that elutes earlier thant-butanol when eluted from a silica gel column.

The sulfur may include sulfur-based materials, sulfur-based compoundsand sulfur-based substances for the safe disposal of waste materials andall toxic substances which have (i) a boiling point greater than thetemperature needed to melt sulfur and (ii) the solubilitycharacteristics in a low-polar solvent that elutes earlier thant-butanol when eluted from a silica gel column including all inorganictoxic substances and all organic toxic substances with (i) a boilingpoint greater than the temperature needed to melt sulfur and (ii) thesolubility characteristics in a low-polar solvent that elutes earlierthan t-butanol when eluted from a silica gel column.

Having described the present invention as related to the presentembodiments, it is the present inventor's intention that the inventionnot be limited by any of the details of the description, unlessotherwise specified, but rather be construed broadly within its spiritand scope as set out in the accompanying claims.

What we claim is:
 1. A process for safe disposal of all toxicsubstances, the process comprising the steps of: (a) providing asulfur-based material; (b) mixing said sulfur-based material with saidtoxic substances; (c) reducing the water content of said mixture; (d)heating said mixture to approximately between 130 to 159° C.; and (e)cooling said mixture, wherein the weight ratio of sulfur to toxicsubstance is in the range of about 1:1×10⁻⁷ to 1:1×10⁻³, wherein saidmixture in step (e) is non-toxic, and wherein said toxic substances havea boiling point higher than the temperature necessary to melt sulfur andthe solubility characteristics in a low-polar solvent, the low-polarsolvent being eluted earlier than t-butanol when eluted from a silicagel column.
 2. The process in accordance with claim 1 wherein said toxicsubstances includes all inorganic toxic substances with a boiling pointgreater than the temperature necessary to melt sulfur and the solubilitycharacteristics in a low-polar solvent, the low-polar solvent beingeluted earlier than t-butanol when eluted from a silica gel column. 3.The process in accordance with claim 1 wherein said toxic substancesincludes all organic toxic substances with a boiling point greater thanthe temperature necessary to melt sulfur and the solubilitycharacteristics in a low-polar solvent, the low-polar solvent beingeluted earlier than t-butanol when eluted from a silica gel column. 4.The process in accordance with claim 1 wherein the process furthercomprises molding said mixture in the step (e), wherein said resultingmixture is non-toxic and reusable.
 5. A process for safe disposal of alltoxic substances, the process comprising the steps of: (a) providing asulfur-based compound; (b) mixing said sulfur-based compound with saidtoxic substances; (c) reducing the water content of said mixture; (d)heating said mixture to approximately between 130 to 159° C.; and (e)cooling said mixture, wherein the weight ratio of sulfur to toxicsubstance is in the range of about 1:1×10⁻⁷ to 1:1×10⁻³, wherein saidmixture in step (e) is non-toxic, and wherein said toxic substances havea boiling point higher than the temperature necessary to melt sulfur andthe solubility characteristics in a low-polar solvent, the low-polarsolvent being eluted earlier than t-butanol when eluted from a silicagel column.
 6. The process in accordance with claim 5 wherein said toxicsubstances includes all inorganic toxic substances which have a boilingpoint greater than the temperature necessary to melt sulfur and thesolubility characteristics in a low-polar solvent, the low-polar solventbeing eluted earlier than t-butanol when eluted from a silica gelcolumn.
 7. The process in accordance with claim 5 wherein said toxicsubstances includes all organic toxic substances which have a boilingpoint greater than the temperature necessary to melt sulfur and thesolubility characteristics in a low-polar solvent, the low-polar solventbeing eluted earlier than t-butanol when eluted from a silica gelcolumn.
 8. The process in accordance with claim 5 wherein the processfurther comprises molding said mixture in the step (e), wherein saidresulting mixture is non-toxic and reusable.
 9. A process for safedisposal of all toxic substances, the process comprising the steps of:(a) providing a sulfur-based substance; (b) mixing said sulfur-basedsubstance with said toxic substances; (c) reducing the water content ofsaid mixture; (d) heating said mixture to approximately between 130 to159° C.; and (e) cooling said mixture, wherein the weight ratio ofsulfur to toxic substance is in the range of about l:1×10⁻⁷ to l:1×10⁻³,wherein said mixture in step (e) is non-toxic, and wherein said toxicsubstances have a boiling point higher than the temperature necessary tomelt sulfur and the solubility characteristics in a low-polar solvent,the low-polar solvent being eluted earlier than t-butanol when elutedfrom a silica gel column.
 10. The process in accordance with claim 9wherein said toxic substances includes all inorganic toxic substanceswhich have a boiling point greater than the temperature necessary tomelt sulfur and the solubility characteristics in a low-polar solvent,the low-polar solvent being eluted earlier than t-butanol when elutedfrom a silica gel column.
 11. The process in accordance with claim 9wherein said toxic substances includes all organic toxic substanceswhich have a boiling point greater than the temperature necessary tomelt sulfur and the solubility characteristics in a low-polar solvent,the low-polar solvent being eluted earlier than t-butanol when elutedfrom a silica gel column.
 12. The process in accordance with claim 9wherein the process further comprises molding said mixture in the step(e), wherein said resulting mixture is non-toxic and reusable.
 13. Aprocess for safe disposal of all toxic substances, the processcomprising the steps of: (a) providing sulfur; (b) mixing said sulfurwith said toxic substances; (c) reducing the water content of saidmixture; (d) heating said mixture to approximately between 130 to 159°C.; and (e) cooling said mixture, wherein the weight ratio of sulfur totoxic substance is in the range of about l:1×10⁻⁷ to l:1×10⁻³, whereinsaid mixture in step (e) is non-toxic, and wherein said toxic substanceshave a boiling point higher than the temperature necessary to meltsulfur and the solubility characteristics in a low-polar solvent, thelow-polar solvent being eluted earlier than t-butanol when eluted from asilica gel column.
 14. The process in accordance with claim 13 whereinsaid toxic substances includes all inorganic toxic substances which havea boiling point greater than the temperature necessary to melt sulfurand the solubility characteristics in a low-polar solvent, the low-polarsolvent being eluted earlier than t-butanol when eluted from a silicagel column.
 15. The process in accordance with claim 13 wherein saidtoxic substances includes all organic toxic substances which have aboiling point greater than the temperature necessary to melt sulfur andthe solubility characteristics in a low-polar solvent, the low-polarsolvent being eluted earlier than t-butanol when eluted from a silicagel column.
 16. The process in accordance with claim 13 wherein theprocess further comprises molding said mixture in the step (e), whereinsaid resulting mixture is non-toxic and reusable.
 17. The process inaccordance with claim 13 wherein said sulfur is provided by sulfur-basedmaterials.
 18. The method in accordance with claim 13 wherein saidsulfur is provided by sulfur-based compounds.
 19. The method inaccordance with claim 13 wherein said sulfur is provided by sulfur-basedsubstances.